As our society becomes more mobile and information dependent the demand for untethered data communications continues to grow. A proliferation of radio data communications systems have been, are being, or will be deployed in an attempt to satisfy this demand. To no ones surprise, these systems, while often occupying or providing coverage to overlapping geographic areas and user groups, do not always lend themselves to providing alternative seamless data message delivery service to a particular user's terminal.
The systems, as deployed and planned, have sought to optimize different criteria depending on the system designers perception of what user groups needs are intended to be addressed by a particular radio data communications system. Such criteria have included various combinations of data message delivery capacity and delivery reliability, conservation of radio frequency spectrum, system deployment economics, and the extent of the desired geographic coverage. The process of optimization often relies on or takes advantage of expected or measured characteristics and content of data messages that are representative of probable system traffic. As a result of the above considerations at least two distinct types of systems, often referred to as a single frequency and multiple frequency reuse systems respectively, have evolved to provide data message delivery to user groups throughout a geographic area.
While distinct, both systems include some similar elements, functions, or characteristics. For example, both systems (networks) likely are centrally managed under the control of a network controller and include a plurality of fixed (base) stations arranged and managed to provide data message delivery to portable stations (portable or mobile terminals) throughout a geographic area. The network controller includes, among others, a data message routing function for selecting the appropriate path to attempt a data message delivery to a particular portable station. This path selection will depend in part on an estimate of the geographic location of the particular portable station or other system activity and may include when to attempt a data message delivery, which base station to utilize, and therefore, or additionally, which radio channel (a radio channel may represent two radio frequencies, one for receive and one for transmit).
One of these systems, referred to as a multi-frequency reuse (MFR) system, is characterized by typically comparatively small coverage areas with adjacent areas employing different radio channels, thus frequencies, and spatially distant areas reusing the same radio channels. The areas in total provide coverage throughout the intended MFR geographic area. Ordinarily the fixed stations, at least one per area, in this system are continuously transmitting and receiving and portable stations are capable of operating on any legitimate network channel. The portable stations, by scanning the network channels, etc., can determine or aid in determining there location within the intended MFR geographic area by observing the better quality channels based on signal strength, error rates, etc. The MFR network, although using several radio channels and thus frequencies, can provide significant data message delivery capacity since all areas may be simultaneously and independently active. Said another way, any path within the MFR system will, at least in principle, have a unique radio channel, i.e. frequency.
The second system, referred to as a single frequency reuse (SFR) system, is characterized by a multiplicity of coverage areas where all areas and potential paths are served by the same radio channel. As above, the areas in total provide coverage throughout the intended SFR geographic area. The fixed stations, usually one per area, in the SFR system are not ordinarily all simultaneously and independently active. To demonstrate, since all areas and paths operate on the same radio channel any two or more areas, when simultaneously active (respective fixed stations transmitting), will have an interference region. This region's geographic size and boundary will depend in part on the spatial separation, radio power levels, etc., of the respective base stations. Within this interference region a given portable station likely cannot resolve (successfully receive) a data message from either of the stations.
In essence the effective coverage area depends at least in part on activity within other areas of the SFR system. Portable stations used in the SFR system need only operate on the assigned channel for the network and will not be able to directly aid in determining their location within the intended SFR geographic area unless and until the appropriate fixed station is enabled and uniquely identified. The SFR network tends to be viewed as a spectrally efficient and cost effective approach to providing coverage to a comparatively large geographic area. This follows from the limited number of frequencies employed and comparative simplicity of the portable stations, etc. Somewhat offsetting the above noted attributes, resulting from the single channel, interference regions, etc., a SFR system will typically have relatively limited data message delivery capacity and often more complicated data message routing functions.
These differences in data communications networks have here-to-fore made it impossible or unduly burdensome to provide alternative seamless data message delivery to a particular user from either of the two types of systems. It is not economically effective or ergonomically practical for a user to carry two portable stations, one each configured to operate on each system. Manual selection of the appropriate system at a portable station configured to operate on either system, while possible, does not assure seamless (at least in time if at all) coverage to the user. Therefore an urgent need exists, that is becoming more evident, for inventive data communications that automatically provide seamless data message delivery to a user regardless of network configuration.